Re: low profile
Wed, 16 Oct 96 14:07:11 GMT

Robin Hanson wrote:
>could someone nova our star, or galactic centre?

Forrest Bishop: wrote:
>Yes [then a story about inducing a fusion reaction in the
outer layers of the sun]

Does not sound plausible to me. First, if you would
literally nova our "star" you would have to increase its
mass by 40% -quite a heavy initiator! Even so, you would
presumably have to wait millions of years before the sun had
burned up its hydrogen fuel (and then helium etc) and begun
to contract.

If you wanted to induce an explosion by sending a bomb to
the precritical region surounding the core, I don't think
this would work either. The sun shines by hydrogen burning;
there are enormous fusion bombs detonating in the sun every
second. The balance between Coloumb forces and average
kinetic energy must be quite robust, or stars would blow up
at any time in the middle of their evolution.

As for the galactic centre, it is more difficult to tell, I
believe. I would think that a chain reaction would
presuppose a high denisty of white dwarfs or equivalent.

Moreover, a supernova explodes at only about 15000 km/sec,
which an advanced civilisation could perhaps be possible to
run away from. A lot of the energy is also released in the
form of neutrinos, which travel at approximately the speed
of light; but then again there is a very small cross section
for neutrino reactions, so one could stand a very heavy
neutrino shower without getting hurt.

In general, the effect of any cosmic blast drops off as the
inverse cube of the distance. Since cosmic distances are
typically very large, such indiscriminate blasts would seem
to be ineffective as means of warfare. Even a supernova
explosion, which is about as violent as anything (short of
big bang, or vacum decay or a big chain reaction of
supernovae where such is possible) would not hurt us
significantly if it were a few light years away, and an
armoured civilisation could survive much closer.

An "electomagnetic pulse of unspeakable amplitude" (Forrest
Bishop) would also seem like science fiction proper.

It is important that we use realistic assumptions about the
conditions of cosmic warfare in our simulations. Since there
are still many unsolved problems in fundamental physics, I
suggest we set up several simulations with different
parameters for weapon technology. There are several relevant
variables here, such as projectile speed, production cost,
identifiability of aggressor, technology level required for
its manufacture, discrimination capabilities ("hurt only the
bad guys"), etc. Maybe the time is ripe to begin to try to
really work this out.

Nicholas Bostrom